Roguelike

Roguelike is a genre of games characterised by key gameplay elements pioneered by the 1980 game, Rogue.

Spelunky is not a 'pure' roguelike. It is a cross-genre game (also known as a 'Rogue-lite' or 'Roguelike-like') that is partly defined by roguelike elements, but differs from the genre in certain aspects.

Spelunky's roguelike elements include:

Permanent death — games can't be saved/loaded, and death means you must start from the beginning of the game.

Procedurally generated levels that are wholly unpredictable.

Relatively high difficulty, with frequent deaths and short runs.

It's a dungeon crawl, which takes place by progressing along rigidly defined 'levels' of the cave.

Ways in which Spelunky differs from traditional roguelikes include:

It's a side-scrolling platformer, rather than a top-down Dungeon Crawl.